The Jeet Kune Do Emblem
The Taijitu represents the concepts of yin and yang. The Chinese characters indicate: "Using no way as way" & "Having no limitation as limitation". The arrows represent the endless interaction between yang and yin.[1]

Jeet Kune Do, abbreviated JKD[citation needed], is an eclectic and hybrid style fighting art heavily influenced by the philosophy of martial artist Bruce Lee, who founded the system in 1967, referred it as "non-classical", suggesting that JKD is a form of Chinese Kung Fu, yet without form. Unlike more traditional martial arts, Jeet Kune Do is not fixed or patterned, and is a philosophy with guiding thoughts. It was named for the Wing Chun concept of interception or attacking while one's opponent is about to attack. Jeet Kune Do practitioners believe in minimal movements with maximum effects and extreme speed. The system works by using different "tools" for different situations, where the situations are divided into ranges, which are kicking, punching, trapping, and grappling, where martial artists use techniques to flow smoothly between them.

In the screenplay of the 1973 Warner Brothers film, Enter the Dragon, when Lee is asked, "What's your style?" Lee replied, "My style?...You can call it the art of fighting without fighting." Thus one may also ideologically define JKD simply as the Bruce Lee Kung Fu or the Bruce Lee style of Kung Fu.

The name Jeet Kune Do was often said by Lee to be just a name, and he often referred to it as "the art of expressing the human body" in his writings and in interviews. Through his studies Lee came to believe that styles had become too rigid and unrealistic. He called martial art competitions of the day "dry land swimming". He believed real combat was spontaneous, and a martial artist can not predict it, but, only react to it, and a good martial artist should "be like water"—move fluidly without hesitation.

In 2004, the Bruce Lee Foundation decided to use the name Jun Fan Jeet Kune Do (振藩截拳道) to refer to the martial arts system which Lee founded; "Jun Fan" being Lee's Chinese given name.

Originally, when Lee began researching various fighting styles, he called it Jun FanGung Fu. However, not wanting to create another style which would share the limitations that all styles had, he instead described the process which he used to create it:

I have not invented a "new style," composite, modified or otherwise that is set within distinct form as apart from "this" method or "that" method. On the contrary, I hope to free my followers from clinging to styles, patterns, or molds. Remember that Jeet Kune Do is merely a name used, a mirror in which to see "ourselves". . . Jeet Kune Do is not an organized institution that one can be a member of. Either you understand or you don't, and that is that.

There is no mystery about my style. My movements are simple, direct and non-classical. The extraordinary part of it lies in its simplicity. Every movement in Jeet Kune Do is being so of itself. There is nothing artificial about it. I always believe that the easy way is the right way. Jeet Kune Do is simply the direct expression of one's feelings with the minimum of movements and energy. The closer to the true way of Kung Fu, the less wastage of expression there is. Finally, a Jeet Kune Do man who says Jeet Kune Do is exclusively Jeet Kune Do is simply not with it. He is still hung up on his self-closing resistance, in this case anchored down to reactionary pattern, and naturally is still bound by another modified pattern and can move within its limits. He has not digested the simple fact that truth exists outside all molds; pattern and awareness is never exclusive. Again let me remind you Jeet Kune Do is just a name used, a boat to get one across, and once across it is to be discarded and not to be carried on one's back.

JKD as it survives since then—if one views it "refined" as a product, not a process—is what was left at the time of Lee's death. It is the result of the lifelong martial arts development process Lee went through. Lee stated his concept does not add more and more things on top of each other to form a system, but rather selects the best thereof. The metaphor Lee borrowed from ChanBuddhism was of constantly filling a cup with water, and then emptying it, used for describing Lee's philosophy of "casting off what is useless". He used the sculptor's mentality of beginning with a lump of clay and removing the material which constituted the "unessentials"; the end result was what he considered to be the bare combat essentials, or JKD. The dominant or strongest hand should be in the lead because it would perform a greater percentage of the work. Lee minimized the use of other stances except when circumstances warranted such actions.

Although the On-Guard position is a formidable overall stance, it is by no means the only one. He acknowledged there were times when other positions should be utilised. Lee felt the dynamic property of JKD was what enabled its practitioners to adapt to the constant changes and fluctuations of live combat. He believed these decisions should be made within the context of "real combat" and/or "all out sparring" and that it was only in this environment that a practitioner could actually deem a technique worthy of adoption. Lee believed that real combat was alive and dynamic. Circumstances in a fight change from millisecond to millisecond. Thus, pre-arranged patterns and techniques are not adequate in dealing with such a changing situation. As an antidote to this line of thought, Lee once wrote an epitaph which read: 'In memory of a once fluid man, crammed and distorted by the classical mess.' The "classical mess" in this instance was what Lee thought of the "not too alive way of the classical kung fu styles".[5]

The following are principles that Lee incorporated into Jeet Kune Do.[6] Lee felt these were universal combat truths that were self-evident, and would lead to combat success if followed. Familiarity with each of the "Four ranges of combat", in particular, is thought to be instrumental in becoming a "total" martial artist. JKD teaches that the best defense is a strong offense, hence the principle of an "intercepting fist". For someone to attack another hand-to-hand, the attacker must approach the target. This provides an opportunity for the attacked person to "intercept" the attacking movement. The principle of interception may be applied to more than intercepting physical attacks; non-verbal cues (subtle movements that an opponent may be unaware of) may also be perceived or "intercepted", and thus be used to one's advantage. The "Five ways of attack", categories which help JKD practitioners organize their fighting repertoire, comprise the offensive teachings of JKD. The concepts of "Stop hits & stop kicks", and "Simultaneous parrying & punching", based on the concept of single fluid motions which attack while defending (in systems such as Épée fencing and Wing Chun), compose the defensive teachings of JKD. These concepts were modified for unarmed combat and implemented into the JKD framework by Lee to complement the principle of interception.

Lee felt that the straight lead was the most integral part of Jeet Kune Do punching, as he stated, "The leading straight punch is the backbone of all punching in Jeet Kune Do."[2] The straight lead is not a power strike but a strike formulated for speed. The straight lead should always be held loosely with a slight motion, as this adds to its speed and makes it more difficult to see and block. The strike is not only the fastest punch in JKD, but also the most accurate. The speed is attributed to the fact that the fist is held out slightly making it closer to the target and its accuracy is gained from the punch being thrown straight forward from one's centerline. The straight lead should be held and thrown loosely and easily, tightening only upon impact, adding to one's punch. The straight lead punch can be thrown from multiple angles and levels.[7]

Lee felt explosive attacks with no telegraphing signs of intention were best. He argued that the attacks should catch the opponent off-guard, throwing them off their balance and leaving them unable to defend against further attacks. "The concept behind this is that when you initiate your punch without any forewarning, such as tensing your shoulders or moving your foot or body, the opponent will not have enough time to react," Lee wrote.[8] The key is that one must keep one's body and arms loose, weaving one's arms slightly and only becoming tense upon impact. Lee wanted no wind-up movements or "get ready poses" to prelude any JKD attacks. Lee explained that any twitches or slight movements before striking should be avoided as they will give the opponent signs or hints as to what is being planned and then they will be able to strike first while one is preparing an attack. Consequently, non-telegraphed movement is an essential part of Jeet Kune Do philosophy.[9]

Lee emphasized that every situation, in fighting or in everyday life, is varied. To obtain victory, therefore, it is essential not to be rigid, but to be fluid and able to adapt to any situation. He compared it to being like water: "Empty your mind, be formless, shapeless, like water. If you put water into a cup, it becomes the cup. You put water into a bottle and it becomes the bottle. You put it in a teapot it becomes the teapot. That water can flow, or it can crash. Be water, my friend."[10] Lee’s theory behind this was that one must be able to function in any scenario one is thrown into and should react accordingly. One should know when to speed up or slow down, when to expand and when to contract, and when to remain flowing and when to crash. It is the awareness that both life and fighting can be shapeless and ever changing that allows one to be able to adapt to those changes instantaneously and bring forth the appropriate solution. Lee did not believe in "styles" and felt that every person and every situation is different and not everyone fits into a mold; one must remain flexible in order to obtain new knowledge and victory in both life and combat. One must never become stagnant in the mind or method, always evolving and moving towards improving oneself.[11]

Jeet Kune Do seeks to waste no time or movement, teaching that the simplest things work best, as in Wing Chun. Economy of motion is the principle by which JKD practitioners achieve:

Efficiency: An attack which reaches its target in the least amount of time, with maximum force.

Directness: Doing what comes naturally in a disciplined way.

Simplicity: Thinking in an uncomplicated manner; without ornamentation.

This is meant to help a practitioner conserve both energy and time, two crucial components in a physical confrontation. Maximized force seeks to end the battle quickly due to the amount of damage inflicted upon the opponent. Rapidity aims to reach the target before the opponent can react, which is half-beat faster timing, as taught in Wing Chun and Western boxing.[12] Learned techniques are utilized in JKD to apply these principles to a variety of situations.

"When the distance is wide, the attacking opponent requires some sort of preparation. Therefore, attack him on his preparation of attack." "To reach me, you must move to me. Your attack offers me an opportunity to intercept you." This means intercepting an opponent's attack with an attack of one's own instead of simply blocking it. It is for this concept Jeet Kune Do is named. JKD practitioners believe that this is the most difficult defensive skill to develop. This strategy is a feature of some traditional Chinese martial arts as Wing Chun, as well as an essential component of European Épée Fencing. Stop hits and kicks utilize the principle of economy of motion by combining attack and defense into one movement, thus minimizing the "time" element.[13]

When confronting an incoming attack, the attack is parried or deflected, and a counterattack is delivered at the same time. This is not as advanced as a stop hit but more effective than blocking and counterattacking in sequence. This is practiced by some Chinese martial arts such as Wing Chun, and it is also known in Krav Maga as "bursting". Simultaneous parrying & punching utilizes the principle of economy of motion by combining attack and defense into one movement, thus minimizing the "time" element and maximising the "energy" element. Efficiency is gained by utilizing a parry rather than a block. By definition a "block" stops an attack, whereas a parry merely re-directs it. Redirection has two advantages, first that it requires less energy to execute and second that it utilizes the opponent's energy against them by creating an imbalance. Efficiency is gained in that the opponent has less time to react to an incoming attack, since they are still nullifying the original attack.

JKD practitioners believe they should direct their kicks to their opponent's shins, knees, thighs, and midsection, as in Wing Chun.[14] These targets are the closest to the foot, provide more stability and are more difficult to defend against. Maintaining low kicks utilizes the principle of economy of motion by reducing the distance a kick must travel, thus minimizing the "time" element. However, as with all other JKD principles nothing is "written in stone". If a target of opportunity presents itself, even a target above the waist, one could take advantage and not be hampered by this principle.

Jeet Kune Do students train in each of the aforementioned ranges equally. According to Lee, this range of training serves to differentiate JKD from other martial arts. Lee stated that most but not all traditional martial arts systems specialize in training at one or two ranges. Lee's theories have been especially influential and substantiated in the field of mixed martial arts, as the MMA Phases of Combat are essentially the same concept as the JKD combat ranges. As a historic note, the ranges in JKD have evolved over time. Initially the ranges were categorized as short or close, medium, and long range.[3] These terms proved ambiguous and eventually evolved into their more descriptive forms, although some may still prefer the original three categories.

An animation of mechanical linkage to the shoulders of the triangle illustrates the importance of guarding the centerline.

The centerline is an imaginary line drawn vertically along the center of a standing human body, and refers to the space directly in front of that body. If one draws an isosceles triangle on the floor, for which one's body forms the base, and one's arms form the equal legs of the triangle, then h (the height of the triangle) is the centerline. The Wing Chun concept is to exploit, control and dominate an opponent's centerline. All attacks, defenses, and footwork are designed to guard one's own centerline while entering the opponent's centerline space. Lee incorporated this theory into JKD from his SifuYip Man's Wing Chun.[15]

The three guidelines for centerline are:

The one who controls the centerline will control the fight.

Protect and maintain your own centerline while you control and exploit your opponent's.

Control the centerline by occupying it.

This notion is closely related to maintaining control of the center squares in the strategic game chess. The concept is naturally present in xiangqi (Chinese chess), where an "X" is drawn on the game board, in front of both players' general and advisors.[15]

One of the premises that Lee incorporated in Jeet Kune Do was "combat realism". He insisted that martial arts techniques should be incorporated based upon their effectiveness in real combat situations. This would differentiate JKD from other systems where there was an emphasis on "flowery technique", as Lee would put it. Lee claimed that flashy "flowery techniques" would arguably "look good" but were often not practical or would prove ineffective in street survival and self-defense situations. This premise would differentiate JKD from other "sport"-oriented martial arts systems that were geared towards "tournament" or "point systems". Lee felt that these systems were "artificial" and fooled their practitioners into a false sense of true martial skill. Lee felt that because these systems favored a "sports" approach they incorporated too many rule sets that would ultimately handicap a practitioner in self-defense situations. He felt that this approach to martial arts became a "game of tag" which would lead to bad habits such as pulling punches and other attacks; this would again lead to disastrous consequences in real world situations.[16]

Another aspect of realistic martial arts training fundamental to JKD is what Lee referred to as "aliveness". This is the concept of training techniques with an unwilling assistant who offers resistance. Lee made a reference to this concept in his famous quote "Boards don't hit back!"[17] Because of this perspective of realism and aliveness, Lee utilized safety gear from various other contact sports to allow him to spar with opponents "full out". This approach to training allowed practitioners to come as close as possible to real combat situations with a high degree of safety.

Although Lee officially closed his martial arts schools two years before his death, he allowed his curriculum to be taught privately. Since his death, Jeet Kune Do is argued to have split into different groups. Allegedly they are:

The Original (or Jun Fan) JKD branch, whose proponents include Taky Kimura, James Yimm Lee, Jerry Poteet, Bob Bremer, and Ted Wong; these groups teach what was developed and taught by Lee, and encourage the student to further develop his or her self and abilities through those teachings. The inherent training principles of this branch are shaped by the concepts of what was "originally taught", by Lee, which does include concepts that are often misused and misunderstood. Some argue these theories are merely viewed in different contexts by the two branches.

The JKD Concepts branch, whose proponents include Dan Inosanto, Richard Bustillo, and Larry Hartsell; these groups strive to continue the philosophy of individual self-expression through re-interpretation of combat systems through the lens of Jeet Kune Do, under the concept that it was never meant to be a static art but rather an ongoing evolution, and have incorporated elements from many other martial arts into the main fold of its teachings (most notably, grappling and Kali/Escrima material) based on the individual's personal preferences and physical attributes. The entire "system" can be described through a simple diagram, and the concepts can then be applied to a variety of contexts in a "universal" way.

As far as is known, Lee himself authorized only one person to teach Jeet Kune Do: Daniel Inosanto, who achieved 3rd rank in JKD. Ted Wong, Lee's last student, achieved 2nd rank in Jeet Kune Do while training privately with Lee. After this, Lee did away with rankings in his teachings, so Ted was never "ranked" beyond the 2nd. Dan Inosanto, however, fully certified Ted Wong to teach after Lee's death.

Two other people were certified to teach by Lee as well. Taky Kimura and James Yimm Lee were certified to teach Jun Fan Gung Fu (the precursor to JKD), but not Jeet Kune Do itself.

There are essentially two "types" or viewpoints of Jeet Kune Do:

JKD Framework This type of JKD provides the guiding principles. Lee experimented with many styles and techniques to reach these conclusions. To Lee these principles were truisms. The JKD framework is not bound or confined by any styles or systems. This type of JKD is a process.

JKD Personal Systems This type of JKD utilizes the JKD framework along with any techniques from any other style or system to construct a "personal system". This approach utilizes a "building blocks" manner in which to construct a personalized system that is especially tailored to an individual. Lee believed that only an individual could determine for oneself what the usefulness of any technique should be. This type of JKD is thus a product, but left to personal interpretation and therefore drifts further from what Lee actually developed and employed.

Lee believed that this freedom of adoption was a distinguishing property from traditional martial arts.

There are many who confuse the JKD Framework with a JKD Personal System (i.e. Lee's personal JKD) thinking them to be one and the same. The system that Lee personally expressed was his own personal JKD; that is, tailored for himself. Before he could do this, however, he needed to first develop the "JKD Framework" process. Many of the systems that Lee studied were not to develop his "Personal JKD" but rather to gather the "principles" for incorporation in the JKD Framework approach. The uniqueness of JKD to Lee is that it was a "process", not a "product", and thus not a "style" but a system, concept, or approach. Traditional martial arts styles are essentially a product that is given to a student with little provision for change. These traditional styles are usually fixed and not tailored for individuals. Lee said there were inherent problems with this approach and established a "process" based system rather than a fixed style which a student could then utilize to make a "tailored" or "personal" product of their own. To use an analogy: traditional martial arts give students fish to eat (a product), but Lee believed that a martial art should just teach the student to fish (a process) and gain the food directly.

The two branches of JKD differ in what should be incorporated or offered within the "JKD Framework". The Original (or Jun Fan) JKD branch believes that the original principles before Lee died are all that is needed for the construction of personalized systems. The JKD Concepts branch believe that there are further principles that can be added to construct personalized systems. The value of each Branch can be determined by individual practitioners based on whatever merits they deem important.

Original JKD is further divided into two points of view, which both hold Wing Chun, Western boxing, and fencing as the cornerstones of Lee's JKD.

OJKD follows all Lee's training from early Jun Fan Gung Fu (Seattle period) and focuses on trapping with Wing Chun influence. This is his teachings before they were Jeet Kune Do, but still his kung fu interpretations.

Jun Fan Jeet Kune Do is a signature version of JKD as Lee taught privately to Ted Wong. This is a later time period and practices a greater emphasis on elusiveness and simplified trapping unique to Lee's later approach to combat. The focus is with Wing Chun, Western Boxing, and Épée Fencing.

In the fighting video-game series Tekken, the characters Lee Chaolan, Marshall Law (Tekken), and Forest Law all use Jeet Kune Do. The characters Marshall and Forrest Law themselves are homages to Bruce and Brandon Lee, respectively.

In the fighting video-game series Virtua Fighter the character Jacky Bryant uses Jeet Kune Do.

In the fighting video game series Dead or Alive the character Jann Lee also uses Jeet Kune Do.

In the fighting video game series Street Fighter, the character Fei Long uses a fictional system called Hitenryu derived from JKD. It incorporates many elements from Jeet Kune Do as the character is also a homage to Bruce Lee.

In the popular manga, Detective Conan, Sera Masumi is mentioned to have learnt Jeet Kune Do.

In the The Bourne Ultimatum (film) movie, some moves that combined Filipino Kali and JKD were used in the fighting sequence, as introduced in the special features in the Bourne Ultimatum DVD, by Jeff Imada, Fight Stunt Coordinator for the Bourne Identity/Supremacy/Ultimatum, with the intent to have proven-in-combat techniques and very fast executions that can take care of opponents as quickly as possible.